1. Field of the Invention
The present invention relates to an ink jet recording head, and in particular, to an ink jet recording head cartridge which integrally comprises a container for retaining a liquid (ink) used for recording.
2. Description of the Related Art
An ink jet recording head generally has a plurality of discharge energy generating elements which generate energy for discharging an ink, and a plurality of nozzles leading to a plurality of discharge ports which discharge the ink through the discharge energy generating elements. It is known that heater elements are used as the discharge energy generating elements, and in this case, a liquid is bubbled by the heater elements, and a pressure produced thereby is utilized to discharge the ink. The ink jet recording head using such heater elements are easy in size reduction, and a part including the heater elements and nozzles may be configured as a small-sized heating circuit section. Such an ink jet recording head may further be configured as an ink jet recording head cartridge which integrally comprises a container for retaining the ink, and a member forming a flow path for providing the ink from the container to the heating circuit section.
In the flow path of such an ink jet recording head cartridge, bubbles tend to accumulate inside due to air entering inside the flow path, especially entering under the influence of environmental changes, air remaining in the ink, air separated from the ink as the ink is heated by the heater elements, air mixed in the flow path in a head manufacturing process, and the like. When many bubbles are produced inside the flow path, they interrupt the ink supply to a heater element section, so that sufficient supply of ink may not be possible, and especially, if the bubbles grow into large fixed bubbles in an ink supply passage, they can cause a problem that the ink supply passage is substantially completely blocked by the bubbles temporarily. Further, if the bubbles are scattered on the heater elements, they prevent predetermined bubbling, and the pressure to discharge the ink is absorbed by shrinkage of the bubbles due to so-called damper effects, which might prevent a predetermined ink discharge operation. In this way, the bubbles accumulated in the ink flow path of the cartridge may cause defective recording.
Various methods have heretofore been used to reduce adverse effects of the bubbles accumulated in the flow path as described above. As such methods, a method of reducing a dissolved gas in the ink by deaeration, a method of providing a vapor-liquid separation film inside the ink supply passage, and the like have been known. Moreover, as a method of physically removing the bubbles, a method of removing the bubbles by pumping them together with the ink from the discharge port has been known, and an attempt is also made to make components of the ink easy to debubble. In addition, a specification of U.S. Pat. No. 5,812,165 discloses a method in which the bubbles are retained under a filter, which does not let relatively enlarged bubbles, by use of buoyancy of the bubbles at a vertical portion of the ink supply passage, thereby reducing the bubbles remaining on a further downstream side.
In the above-mentioned method of removing the dissolved gas by deaeration, its manufacturing process is complicated. Moreover, as it is necessary to maintain a state with no air infiltrating into an ink supply system also in actual use, a cartridge configuration is complicated. Further, even with the configuration that reduces the air infiltration, it is difficult to completely prevent air from infiltrating from a cartridge material surface and the discharge port over time, and it is also difficult to maintain a substantially deaerated state over time.
In the method of providing the vapor-liquid separation film, it is necessary to provide a space to dispose this film inside the supply system, and especially necessary to dispose it in the vicinity of the nozzles in order to reduce effects of the bubbles entering from the ink discharge port, so that the cartridge configuration is complicated.
When the method of removing the bubbles by suction, the flow path preferably has a shape or the like that makes it easy to remove the bubbles by suction. However, even this can not avoid a certain amount of ink consumption in addition to bubble removal when suction is used. Moreover, a suction mechanism, an absorbing member to retain the sucked ink in a printer main unit, and the like are required, resulting in an increase in costs of the printer main unit. Further, the ink might also be sucked in a portion where the bubbles are not produced, depending on a shape of a suction system, which might increase the amount of ink to be disposed of, and place an additional burden on users.
In the method of retaining the bubbles under the filter provided in the vertical portion of the ink supply passage as disclosed in the specification of U.S. Pat. No. 5,812,165, if the bubbles grow above a certain level, the ink supply may conceivably be blocked. Especially, in a configuration described in the specification of U.S. Pat. No. 5,812,165, a step portion is provided under the filter in the vertical portion of the ink supply passage, and if the bubbles grow beyond a space surrounded by the step portion and the filter, the ink supply may conceivably be more easily blocked. In addition, if a gas grows up to a horizontal portion of the ink supply passage, the ink supply may conceivably be blocked in the configuration described in the specification of U.S. Pat. No. 5,812,165.
A significant speed increase has been recently achieved in the ink jet recording head, and therefore, the amount of ink required per unit time has been increasing. For this reason, adverse effects on a recording operation due to the bubbles preventing the ink supply as described above have become a greater problem, and even if a greater amount of ink is supplied per unit time, it is even more necessary to prevent a supply amount shortage.